Asked By: Mia LeeUpdated: 30th June 2021

Why are combustion reactions exothermic?

Category: ResearchViews: 112
Combustion is an oxidation reaction that produces heat, and it is therefore always exothermic. Common combustion reactions break the bonds of hydrocarbon molecules, and the resulting water and carbon dioxide bonds always release more energy than was used to break the original hydrocarbon bonds.

Besides, is the combustion reaction in a car engine endothermic or exothermic?

Whilst many reactions are endothermic those chemical reactions that heat us, e.g. the burning (combustion) of fuels and the combustion of petrol in a car engine are two notable exothermic reactions. Hand warmers are often powered by exothermic chemical reactions.

Secondly, are all reactions with oxygen combustion?

Yes,A combustion reaction is a major class of chemical reactions, commonly referred to as "burning". Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. Inorganic combustion reactions might not form all of the products, but are recognizable by the reaction of oxygen.

What type of reaction is always exothermic?

During an exothermic reaction, energy is constantly given off, often in the form of heat. All combustion reactions are exothermic reactions. During combustion, a substance burns as it combines with oxygen, releasing energy in the form of heat and light.

Is a combustion exothermic?

Combustion is a high-temperature exothermic (heat releasing) redox (oxygen adding) chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.

Why is burning wood exothermic?

Burning wood in air is an exothermic process (it releases heat), but there is an energy barrier, so it requires a bit of heat in the beginning to get the reactions started. This is because it's usually necessary to break some chemical bonds (endothermic) before new stronger bonds can be formed (exothermic).

What is difference between burning and combustion?

The basic difference is that combustion is heating and no flames are produced whereas in burning most of the energy is converted to light energy and this results in less heat energy as compared to combustion. when in a combustion process a flame is produced it is referred to burning.

Is ice melting endothermic or exothermic?

Well, it's a little easier going the other way. Melting ice is endothermic -- you can see this by putting a thermometer in a glass of warm water, adding an ice cube, and watching the temperature go down as the ice melts. The melting process needs heat to proceed and takes it from the warm water.

Is heat of formation endothermic or exothermic?

What is the relation between heat of formation and endothermic reaction? - Quora. In a chemical reaction, if the difference between the heat of formation of the products and the heat of formation of the reactants is positive, the process is called endothermic, as it receives heat in order to be completed.

Is Breathing exothermic reaction?

Exothermic reactions release heat or energy. This glucose combines with oxygen in the cells of our body and provides energy. This reaction is known as respiration. hence,respiration is considered as an exothermic reaction.
Answer and Explanation: Evaporation is an endothermic reaction because the liquid molecules must absorb heat in order to transform into gas molecules.

Why is the combustion of h2 exothermic?

The reaction of hydrogen and oxygen is an exothermic reaction because it liberates more energy than it absorbs. In the same way a gasoline-oxygen mixture requires a spark to ignite.

Is bond breaking exothermic?

Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process. Whether a reaction is endothermic or exothermic depends on the difference between the energy needed to break bonds and the energy released when new bonds form.

Is freezing exothermic?

Fusion, vaporization, and sublimation are endothermic processes, whereas freezing, condensation, and deposition are exothermic processes.

Why is freezing exothermic?

When the water is placed in a freezer, the water slowly loses heat to the surrounding cold air. The water molecules on losing energy begin to move slowly, come closer and pack close enough to change to ice. In this process, the water releases heat to the surroundings, so it is an exothermic process.

What does an exothermic graph look like?

Energy diagrams for endothermic and exothermic reactions
Image of a graph showing potential energy in relation to the process of a chemical reaction. In the case of an exothermic reaction, the reactants are at a higher energy level as compared to the products, as shown below in the energy diagram.

What is an example of endothermic?

These examples could be written as chemical reactions, but are more generally considered to be endothermic or heat-absorbing processes: Melting ice cubes. Melting solid salts. Converting frost to water vapor (melting, boiling, and evaporation, in general, are endothermic processes.

What makes a reaction combustion?

A combustion reaction is when a substance reacts with oxygen and releases a huge amount of energy in the form of light and heat. A combustion reaction always includes a hydrocarbon and oxygen as the reactants and always produces carbon dioxide and water as products.

Is electrolysis exothermic or endothermic?

Electrolysis is a reversal of the spontaneous reaction. The reaction occurs in the opposite direction, so is not exothermic releasing energy, but endothermic.

Is rusting endothermic or exothermic?

Iron rusting is a reaction with oxygen to create iron oxide. Forming bonds is exothermic because it releases energy (vs breaking bonds, which is endothermic because it requires energy).

Which reactions are always endothermic?

  • Photosynthesis.
  • Melting of ice.
  • Evaporating liquid water.
  • Sublimation of carbon dioxide (dry ice)
  • Cracking of alkanes.
  • Thermal decomposition reactions.
  • Electrolytic decomposition of sodium chloride into sodium hydroxide and hydrogen chloride.
  • Dissolving ammonium chloride in water.


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